Why is this defaultIfEmpty choosing ienumerable<char> instead of string?
from a in mainDoc.XPathSelectElements开发者_运维技巧("//AssembliesMetrics/Assembly/@Assembly")
let aVal=a.Value
where aVal.IsNullOrEmpty( )==false&&aVal.Contains(" ")
select aVal.Substring(0, aVal.IndexOf(' '))
into aName
let interestedModules=new[ ] { "Core", "Credit", "Limits", "Overdraft" }
where aName.Contains(".")
let module=
interestedModules
.FirstOrDefault(x => aName
.StartsWith(x, StringComparison.InvariantCultureIgnoreCase))
where module!=null
group aName by module.DefaultIfEmpty() // ienumerable<char>, why?
into groups
select new { Module=groups.Key??"Other", Count=groups.Count( ) };
module
is a string.
String implements IEnumerable<char>
.
You're calling the Enumerable.DefaultIfEmpty
method, which extends IEnumerable<T>
.
This method can never return anything other than an IEnumerable<T>
.
EDIT: If you want to replace null
values of module
with a non-null value, you can use the null-coalescing operator:
group aName by module ?? "SomeValue"
However, module
will never actually be null
, because of the where module!=null
clause.
You should then also remove ??"Other"
from the final select
clause.
Because, in this case, module
is a string:
let module = interestedModules
.FirstOrDefault(x => aName
.StartsWith(x, StringComparison.InvariantCultureIgnoreCase))
When you call any of the IEnumerable extensions on a string, it decomposes into an IEnumerable<char>
.
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